Chapter 14: Light and Reflection 14-1: Characteristics of Light -Electromagnetic Waves:
-White light to the visible eye is actually a spectrum of colors: red, orange, yellow, green, blue, and violet.
-Light waves are classified as electromagnetic waves. -Electromagnetic wavesvary depending on frequency and wavelength, which account for different colors of visible light.
-Electromagnetic waves include radio waves, microwaves, infrared waves, visible light, ultraviolet waves, x rays, and gamma rays. Wavelength and frequency values for each type of wave are on page 521. -All electromagnetic waves move at the speed of light: c- 3.00x10^8 m/s. -The relationship between frequency, wavelength, and speed is as follows:
c=fλ
-Waves can be approximated as rays
-Brightness decreases by the square of the distance from the source- the brightness of light depends on how much light is actually emitted from the source and how the distance from the source.
-The apparent brightness is proportional to the actual brightness of the source divided by the square of the distance between the source and the observer. 14-2: Flat Mirrors
-Reflection is the change in the direction of light.
-The texture of the surface affects how light is reflected.
Diffuse reflection is when light rays reflect in many different directions off of a textured surface.
Specular reflection is when rays are reflected in only one direction off of a smooth surface.
-Incoming and reflected angles are equal; the angle of incidence and the angle of reflection are equal when measured off of the normal line: θ=θ'
-The object distance from a flat mirror, p, and the image distance, q, are equal.
-The virtual image is the image formed by rays that appear to come together at the image point behind the mirror.
-A ray diagram will help predict image location:
14-3: Curved Mirrors Concave Spherical Mirrors
-Concave spherical mirrors focus light to produce a real image.
-The image is determined by the amount which the mirror is curved, or the radius of curvature, R, and the distance to the center of curvature, C.
-The real image is when it becomes unfocused as you move away from the lens.
-To predict image location, use the mirror equation:
1/p+1/q=2/R=1/f
where f is the focal length.
-A concave mirror can also be portrayed through a ray diagram:
-Magnification relates image and object sizes.
-Unlike flat mirrors, curved mirrors' image is magnified.
-The equation to find the magnification of an image is:
M=h'/h=-q/p
where h' is the image height and h is the object height.
-The sign of M effects the image:
Convex Spherical Mirrors
-Convex ray diagrams are a little bit different from concave.
1. Focal point and center of curvature are behind the mirror's surface.
2. A virtual, upright image forms where the three lines intersect.
Parabolic Mirrors
-Parabolic mirrors eliminate spherical aberration, when rays from the principal axis converge at slightly different points on the principal axis.
-By using a mirror with a smaller diameter, the spherical aberration is reduced.
-Items such as telescopes use parabolic mirrors.
Refracting telescopesuse a combination of lenses to form an image.
Reflecting telescopes use a curved mirror and small lenses to form an image.
14-4: Color and Polarization
-Additive colors produce white light when combined.
The picture shows what complimentary colors are formed from what colors in light
The picture shows what colors are made when they are added together. The complimentary colors are those that are opposite of each other. Red is complimentary to cyan, Blue to yellow, and green to magenta. Primary additive colors are red, blue, and green. Primary subtractive colors are magenta, cyan, and yellow.
-Subtractive colors block out all light when added together.
Polarization of Light Waves -Linear polarization is when a beam of light with electric field waves orient in the same direction.
-Light can linearly be polarized through transmission.
-Light can be polarized by reflection and scattering.
Sample Problems:
1. The AM radio band extends from 5.4x10^5 Hz to 1.7x10^6 Hz. What are the longest and shortest wavelengths in tehis frequency range?
2. A concave spherical mirror has a focal length of 10.0 cm. Locate the image of a pencil that is placed upright 30.0 cm from the mirror. Find the magnification of the image. Draw a ray diagram to confirm your answer.
3. An upright pencil is placed in fron tof convex spherical mirror with a focal length of 8.00 cm. an erect image 2.50 cm tall is formed 4.44 cm behind the mirror. find the position of the object, the magnification of the image, and the height of the pencil.
14-1: Characteristics of Light
-Electromagnetic Waves:
-White light to the visible eye is actually a spectrum of colors: red, orange, yellow, green, blue, and violet.
-Light waves are classified as electromagnetic waves.
-Electromagnetic waves vary depending on frequency and wavelength, which account for different colors of visible light.
-Electromagnetic waves include radio waves, microwaves, infrared waves, visible light, ultraviolet waves, x rays, and gamma rays. Wavelength and frequency values for each type of wave are on page 521.
-All electromagnetic waves move at the speed of light: c- 3.00x10^8 m/s.
-The relationship between frequency, wavelength, and speed is as follows:
- c=fλ
-Waves can be approximated as rays-Brightness decreases by the square of the distance from the source- the brightness of light depends on how much light is actually emitted from the source and how the distance from the source.
-The apparent brightness is proportional to the actual brightness of the source divided by the square of the distance between the source and the observer.
14-2: Flat Mirrors
-Reflection is the change in the direction of light.
-The texture of the surface affects how light is reflected.
- Diffuse reflection is when light rays reflect in many different directions off of a textured surface.
- Specular reflection is when rays are reflected in only one direction off of a smooth surface.
-Incoming and reflected angles are equal; the angle of incidence and the angle of reflection are equal when measured off of the normal line: θ=θ'-The object distance from a flat mirror, p, and the image distance, q, are equal.
-The virtual image is the image formed by rays that appear to come together at the image point behind the mirror.
-A ray diagram will help predict image location:
14-3: Curved Mirrors
Concave Spherical Mirrors
-Concave spherical mirrors focus light to produce a real image.
-The image is determined by the amount which the mirror is curved, or the radius of curvature, R, and the distance to the center of curvature, C.
-The real image is when it becomes unfocused as you move away from the lens.
-To predict image location, use the mirror equation:
- 1/p+1/q=2/R=1/f
where f is the focal length.-A concave mirror can also be portrayed through a ray diagram:
-Magnification relates image and object sizes.
-Unlike flat mirrors, curved mirrors' image is magnified.
-The equation to find the magnification of an image is:
- M=h'/h=-q/p
where h' is the image height and h is the object height.-The sign of M effects the image:
Convex Spherical Mirrors
-Convex ray diagrams are a little bit different from concave.
1. Focal point and center of curvature are behind the mirror's surface.
2. A virtual, upright image forms where the three lines intersect.
Parabolic Mirrors
-Parabolic mirrors eliminate spherical aberration, when rays from the principal axis converge at slightly different points on the principal axis.
-By using a mirror with a smaller diameter, the spherical aberration is reduced.
-Items such as telescopes use parabolic mirrors.
14-4: Color and Polarization
-Additive colors produce white light when combined.
The picture shows what colors are made when they are added together. The complimentary colors are those that are opposite of each other. Red is complimentary to cyan, Blue to yellow, and green to magenta.
Primary additive colors are red, blue, and green.
Primary subtractive colors are magenta, cyan, and yellow.
-Subtractive colors block out all light when added together.
Polarization of Light Waves
-Linear polarization is when a beam of light with electric field waves orient in the same direction.
-Light can linearly be polarized through transmission.
-Light can be polarized by reflection and scattering.
Sample Problems:
1. The AM radio band extends from 5.4x10^5 Hz to 1.7x10^6 Hz. What are the longest and shortest wavelengths in tehis frequency range?
2. A concave spherical mirror has a focal length of 10.0 cm. Locate the image of a pencil that is placed upright 30.0 cm from the mirror. Find the magnification of the image. Draw a ray diagram to confirm your answer.
3. An upright pencil is placed in fron tof convex spherical mirror with a focal length of 8.00 cm. an erect image 2.50 cm tall is formed 4.44 cm behind the mirror. find the position of the object, the magnification of the image, and the height of the pencil.
Answers:
1. λ1=5.6x10^2 m
λ2=1.8x10^2 m
2. q= 15 cm
M= -q/p= -15cm/30cm= -.50
3. M=0.444
h= 5.63 cm
Bibliography:
"Holt Online Learning." Holt Online Learning. 5 June 2009 <http://my.hrw.com/tabnav/controller.jsp?isbn=0030724864>.
All pictures were taken from "Holt Online Learning." Holt Online Learning. 5 June 2009 <http://my.hrw.com/tabnav/controller.jsp?isbn=0030724864>.